1. Field of the Invention
The invention relates in general to escalators or moving stairways, and more specifically to new and improved arrangements for guiding passenger conveyors of this type.
2. Description of the Prior Art
An escalator must be accurately guided laterally during its travel about the endless loop. The American National Safety code for escalators ANSI A17.1-1971 Rule 802.3C requires that "the clearance on either side of the steps between the step tread and the adjacent skirt panel shall not be more than three-eighths (3/4) inch." Also, the steps must be laterally guided into the combplates.
Escalators conventionally are laterally guided by upstanding guide portions disposed on the tracks which support the main step wheels or rollers. The sides of the step wheels contact the guide portions on the tracks when a dimensional lateral limit is reached, in either lateral direction. The scuffing action between the sides of the wheels and the guiding portions produces noise and wear, necessitating frequent lubrication in order to reduce the noise and wear to acceptable values.
U.S. Pat. No. 3,682,289, which is assigned to the same assignee as the present application, improved the lateral guiding of the steps by guiding from the back side of the skirts via a plurality of auxiliary wheels which bear against auxiliary guide angle members fastened to the skirts.
In both the conventional and improved lateral guiding arrangements mentioned above, the positions of both the left and righthand guides are critical, requiring jigs and fixtures for accurately positioning the guide angle members on both sides of the escalator during manufacture. Further, the field installation and alignment of both guides is critical.
U.S. Pat. No. 1,956,153 discloses grooving one of the main roller tracks to provide a guide member on each edge of one of the tracks, thus guiding from the inside and outside edges of the main rollers on one side of the escalator, and removing the criticality in the position of the track on the other side of the escalator. This arrangement, however, rapidly wears the inner and outer edges of the guided rollers, as all side thrust is taken by these edges.
In all of the above-mentioned guiding arrangements, upthrust of the endless belt to which the steps are attached is accommodated and limited to a predetermined dimension by upthrust tracks spaced above the main wheels or rollers. If a main wheel lifts off its support track, it is limited in its movement by the spacing between the wheel and the upthrust track. When the main wheel strikes the upthrust track, a force is produced on the wheel which attempts to rotate it in a circumferential direction opposite to its present direction, causing scraping and wear, as well as objectionable vibration and noise.
It would be desirable to provide a new and improved escalator having a lateral guiding arrangement which simplifies the manufacture of the escalator, without offsetting disadvantages, such as increased wear, noise and vibration. It would also be desirable to provide the upthrust limit function without the wear, noise and vibration associated with prior art arrangements.